We are using a pre-denervation technique that enables us to transplant successfully heterotopically and autogenously, whole limb muscles of cats. Most fibers in the transplanted muscle degenerate and then regenerate. The fibers are revascularized and reinnervated and up to 40% of the maximum isometric tension of control muscle is regained. For long term transplants of limb skeletal muscles of cats and dogs, we will determine the time at which the process of regeneration stabilizes and the degree of restoration of normal structure and function in the stabilized transplant compared to a non-denervated non-transplanted control muscle located in the same anatomical site. Through the use of different muscles in the limbs of cats and through the use of dog muscles, we will investigate the influence of the mass of the muscle transplanted on the time necessary for stabilization and on the degree of restoration of normal structure and function. We propose a broad spectrum of descriptive measures of the stabilized transplant which would be compared to data on control muscles from cats and dogs. These measures will enable us to describe the muscle fiber types, the area and distribution muscle fibers, the number of fibers per muscle, the capillary density, distribution of motor end-plates, contractile properties, blood flow, oxygen comsumption from rest up to maximum work rates, and electromyographical characteristics during locomotion. The interpretation of these data should provide information on the physiological environment required for successful regeneration and one should then be able to define procedures that will ensure a successful transplantation. A complete description of the functional capabilities of stabilized transplants and an understanding of the prerequisites for a successful transplantation appears necessary before clinical trials may be instituted safely.